gRPC config stream closed: 14, no healthy upstream

Hi guys,
We are using Istio in GKE cluster and getting the following errors after each pod restart/deployment.

[2020-05-06 11:08:31.249][18][warning][config] [bazel-out/k8-opt/bin/external/envoy/source/common/config/_virtual_includes/grpc_stream_lib/common/config/grpc_stream.h:91]
gRPC config stream closed: 14, no healthy upstream

[Envoy (Epoch 0)] [2020-05-06 11:08:31.249][18][warning][config] [bazel-out/k8-opt/bin/external/envoy/source/common/config/_virtual_includes/grpc_stream_lib/common/config/grpc_stream.h:54] Unable to establish new stream

Then after couple of seconds istio-proxy starting to work with log message
“Envoy is Ready” .
Could you advice which is the cause of that errors ?

The envoy startup time takes 5-6 seconds which is not applicable for applications that should connect to database during startup .